Keyboard

Keyboard is a device for manually entering information into a computer. Modern types of keyboards differ, basically, the principle of signal formation when you press a key. The most common keyboards have under each key a dome made of special rubber, which bends when the key is pressed and closes the contacts with a conductive layer located on the dome. Some keyboards under each key are magnet, which, when pressed, moves and passes through the coil, inducing a self-induction current in it.

The modern keyboard can be wireless, in which the transfer of information in the computer is by means of an infrared sensor, similar to the control panels of various household appliances. This keyboard allows you to work in any convenient place for the user, not tied to the location of the system unit. It is also possible to note the flexible rubber keyboard that works silently, is protected from mechanical and chemical destructive influences, very thin and can be rolled up in the form of a cylinder.

The keyboard processor that processes the signals from the keyboard determines the number of the key that was pressed, the so-called scan code, and the operating system already determine which character or command was entered. This approach allows each key to be associated with more than one character. For example, the alphabetic keyboard keys are associated with four different symbols: lowercase and uppercase Latin and national alphabet characters. The same happens with the control keys. When the key is pressed, the keyboard processor sends a scan code of the key, consisting of two bytes: a byte of the actual scan code and a byte that specifies which additional control keys were pressed while in the special memory of the keyboard in RAM. The control keys include the keys Ctrl, Alt, Shift, which also differ in location: left and right, as well as their combinations. The utility reads these two bytes from the keyboard buffer and passes them to the program, which decides which character or control signal to display. This approach to the processing of keystrokes greatly expands the capabilities of the keyboard when specifying control key combinations or when changing the national alphabet. A special program in the Windows operating system, for example, allows you to change the entire keyboard layout or the national alphabet, or the values of individual keys.

The keyboard provides the user with another interesting feature: entering a character that is not displayed on it. To do this, on the small numeric keypad (it is located on the left), the decimal code of the required character is typed while holding down the Alt key. Thus, you can enter a pseudographics symbol or a control character that is not present on the keyboard.